PROCESS AND PLANT FOR OBTAINING PURE HELIUM

Abstract

The present invention relates to a process for obtaining pure helium using a first membrane separation stage a second membrane separation stage and a third membrane separation stage. The first membrane separation stage is supplied with a first helium-containing feed mixture, the second membrane separation stage with a second helium-containing feed mixture and the third membrane separation stage with a third helium-containing feed mixture a first permeate and a first retentate are formed in the first membrane separation stage, a second permeate and a second retentate in the second membrane separation stage and a third permeate and a third retentate in the third membrane separation stage. The first feed mixture is formed using at least part of a helium-containing starting mixture. The second feed mixture is formed using at least part of the first permeate. The third feed mixture is formed using at least part of the second permeate. The third permeate is at least partly processed by pressure swing adsorption to obtain pure helium and a residual mixture at least some of the residual mixture is used in the formation of the second or third feed mixture.

Claims

1. Process (100, 200) for obtaining pure helium using a first membrane separation stage (1), a second membrane separation stage (2) and a third membrane separation stage (3), where the first membrane separation stage (1) is supplied with a first helium-containing feed mixture, the second membrane separation stage (2) with a second helium-containing feed mixture and the third membrane separation stage (3) with a third helium-containing feed mixture, and where a first permeate and a first retentate are formed in the first membrane separation stage (1), a second permeate and a second retentate in the second membrane separation stage (2) and a third permeate and a third retentate in the third membrane separation stage (3), characterized in that the first feed mixture is formed using at least part of a helium-containing starting mixture, in that the second feed mixture is formed using at least part of the first permeate, in that the third feed mixture is formed using at least part of the second permeate, in that the third permeate is at least partly processed by pressure swing adsorption (10) to obtain the pure helium and a residual mixture, and in that at least some of the residual mixture is used in the formation of the second or third feed mixture.

2. Process (100, 200) according to claim 1, in which at least 80% of the helium present in the first feed mixture is transferred to the first permeate and in which at least 80% of the helium present in the second feed mixture is transferred to the second permeate.

3. Process (100, 200) according to claim 1, in which the third permeate has a content of 20 to 80 mole percent of helium.

4. Process (100, 200) according to claim 1, in which the residual mixture has a content of 10 to 70 mole percent of helium.

5. Process (100, 200) according to claim 1, in which the forming of the first feed mixture using at least some of the starting mixture includes a heating operation.

6. Process (100, 200) according to claim 1, in which the forming of the first feed mixture using at least some of the starting mixture includes a pre-enrichment operation.

7. Process (100, 200) according to claim 1, in which the forming of the second feed mixture using at least some of the first permeate and/or of the third feed mixture using at least some of the second permeate includes a compression operation.

8. Process (100, 200) according to claim 1, in which the forming of the third feed mixture using at least some of the second permeate and/or the forming of the second feed mixture using at least some of the first permeate includes a carbon dioxide removal operation.

9. Process (100, 200) according to claim 1, in which the third permeate is subjected to a depletion of hydrogen before it is at least partly subjected to the pressure swing adsorption.

10. Process (100, 200) according to claim 1, in which the starting mixture used is natural gas.

11. Process (100, 200) according to claim 1, in which the pure helium has a content of at least 99.5 mole percent.

12. Process (100, 200) according to claim 1, in which the first, second and third feed mixtures are each free of fractions of the first and second retentates.

13. Process (100, 200) according to claim 1, in which the forming of the first feed mixture using at least some of the starting mixture includes a compression operation.

14. Plant for obtaining pure helium having a first membrane separation stage (1), a second membrane separation stage (2) and a third membrane separation stage (3), where means set up to supply the first membrane separation stage (1) with a first helium-containing feed mixture, the second membrane separation stage (2) with a second helium-containing feed mixture and the third membrane separation stage (3) with a third helium-containing feed mixture are provided, where the first membrane separation stage (1) is set up to form a first permeate and a first retentate, where the second membrane separation stage (2) is set up to form a second permeate and a second retentate, and where the third membrane separation stage (3) is set up to form a third permeate and a third retentate, characterized by means set up to form the first feed mixture using at least part of a helium-containing starting mixture, to form the second feed mixture using at least part of the first permeate, to form the third feed mixture using at least part of the second permeate, to at least partly process the third permeate by pressure swing adsorption to obtain the pure helium and a residual mixture, and to use at least some of the residual mixture in the formation of the second or third feed mixture.

15. (canceled)

16. Plant for obtaining pure helium by the process according to claim 1, the plant having a first membrane separation stage (1), a second membrane separation stage (2) and a third membrane separation stage (3), where means set up to supply the first membrane separation stage (1) with a first helium-containing feed mixture, the second membrane separation stage (2) with a second helium-containing feed mixture and the third membrane separation stage (3) with a third helium-containing feed mixture are provided, where the first membrane separation stage (1) is set up to form a first permeate and a first retentate, where the second membrane separation stage (2) is set up to form a second permeate and a second retentate, and where the third membrane separation stage (3) is set up to form a third permeate and a third retentate, characterized by means set up to form the first feed mixture using at least part of a helium-containing starting mixture, to form the second feed mixture using at least part of the first permeate, to form the third feed mixture using at least part of the second permeate, to at least partly process the third permeate by pressure swing adsorption to obtain the pure helium and a residual mixture, and to use at least some of the residual mixture in the formation of the second or third feed mixture.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 shows a process according to one embodiment of the invention in the form of a schematic process flow diagram.

[0040] FIG. 2 shows a process according to one embodiment of the invention in the form of a schematic process flow diagram.

DETAILED DESCRIPTION OF THE DRAWINGS

[0041] In the figures, elements that are mutually corresponding in terms of functionality or construction bear corresponding reference numerals and for the sake of clarity are not repeatedly elucidated. The elucidations which follow relate to processes and corresponding plants in the same way. It will be appreciated that corresponding plants/processes may in practice also comprise optional or obligatory further components/process steps. These are not shown in the figures which follow merely for clarity.

[0042] In FIG. 1, a process in one embodiment of the invention is illustrated in the form of a schematic process flow diagram and is collectively labelled 100. In the process 100, a first membrane separation stage 1, a second membrane separation stage 2 and a third membrane separation stage 3 are used.

[0043] The process is supplied with a helium-containing starting mixture A. Using at least some of this helium-containing starting mixture A, for example natural gas, by means of any optional processing steps 4 and with a change in temperature 5, a first feed mixture B is formed, which is supplied to the first membrane separation stage 1. As already elucidated above, the first feed mixture B may, however, in principle also be the same as the starting mixture A, meaning that it is supplied to the first membrane separation stage 1 partly or entirely in unchanged form.

[0044] In the first membrane separation stage 1, a first permeate C and a first retentate D are formed. Using the first permeate C, with compression 6, a second feed mixture E is formed and supplied to the second membrane separation stage 2. The first retentate D, by contrast, is discharged from the process 100.

[0045] In the second membrane separation stage 2, a second permeate F and a second retentate G are formed. Using the second permeate F, with compression 7 and carbon dioxide removal 8, a third feed mixture H is formed and supplied to the third membrane separation stage 3. Like the first retentate D, the second retentate G is also exported from the process 100. The retentates D and G are combined in the example shown.

[0046] In the third membrane separation stage 3, a third permeate I and a third retentate K are formed, and the third permeate I is subjected to a hydrogen removal 9 and then supplied to a pressure swing adsorption 10. The third retentate K may likewise be discharged from the process 100 or be recycled in any desired manner. More particularly, the third retentate K can be combined with the first retentate D and/or the second retentate G.

[0047] In the pressure swing adsorption 10, pure helium L and a residual mixture M are formed. The pure helium L can be discharged from the process as product. In the embodiment of the present invention shown, the residual mixture M is recycled upstream of the second membrane separation stage 2 or of the compression 6, and is especially combined with the first permeate C.

[0048] FIG. 2 shows a process in a further embodiment of the present invention in the form of a schematic process flow diagram collectively labelled 200.

[0049] The process 200 illustrated in FIG. 2 differs from the process 100 illustrated in FIG. 1 essentially in that the residual mixture M is supplied not upstream of the second membrane separation stage 2 but upstream of the third membrane separation stage 3 and is supplied to the compression 7 and the carbon dioxide removal 8.

[0050] However, a corresponding residual mixture M can also be recycled at both positions illustrated in the process 100 or 200. In this context, partial recycling at both positions is especially possible.

[0051] Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

[0052] In the foregoing and in the examples, all temperatures are set forth uncorrected in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.

[0053] The entire disclosures of all applications, patents and publications, cited herein and of corresponding European application No. 170205702, filed Dec. 12, 2017, are incorporated by reference herein.

[0054] The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

[0055] From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.